Such an installation typically comprises a stationary feed channel arranged vertically in the centre of the furnace throat, centred on the vertical axis of the furnace, and a distribution spout for distributing the charged materials arriving via said channel in the furnace. In order to enable appropriate distribution of the charged material, the distribution spout may be rotated about said vertical axis and pivoted about a horizontal axis. To this end, the spout is typically mounted pivotably about said horizontal axis, in a shell mounted coaxially around said feed channel, and rotatably about the vertical axis. The spout is mounted pivotably in the shell by means of trunnions of a generally cylindrical shape with a horizontal axis, to which the spout is secured and which are mounted revolvably about said horizontal axis in bearings integral with the shell. In general, the shell is rotated and the spout pivoted by gear means located in an annular chamber surrounding the shell.
The spout is fixed on either side on radially inner ends, directed towards the vertical axis of the furnace, of the trunnions, which are driven pivotably by means of geared drive means located in said chamber surrounding the shell. Said drive means may act directly on the trunnions by meshing, or by means of arms or levers.
The trunnions therefore have an inner end part which is located inside the shell and is therefore directly exposed to the intense heat prevailing in the shaft furnace. They furthermore receive heat conducted from the spout which is itself entirely exposed to the heat of the furnace. In order to cool the trunnions, and optionally the spout, it is known to circulate cooling water in channels provided in the trunnions, the cooling water being introduced into the trunnions via their outer frontal ends opposite the inner ends to which the spout is fixed. In general, because the trunnions are rotatable, revolving joints mounted axially on the outer frontal ends of the trunnions are used to provide a connection between the channels inside the trunnions and the cooling water feed circuit, stationary on the shell, as in particular shown in DE4216166.
A drive system has recently been developed for pivoting the spout which makes use of epicyclic reduction gears which are directly attached to the outer frontal ends of the trunnions. In practice, the trunnions are directly attached to the output shaft of the reduction gears. As a consequence, the frontal end faces of the trunnions are no longer accessible and therefore the cooling circuit can no longer be connected to the trunnion cooling channels as in the prior art via revolving joints fixed to said outer frontal ends.